Laminate structure and boat hull made therefrom

ABSTRACT

A laminate structure and an aluminum open-hulled boat made therefrom. In one embodiment of the laminate structure, an aluminum outer hull layer has adhered thereto a resilient foam layer for absorbing energy that deforms the aluminum outer hull layer. In another embodiment, the laminate structure includes a harder supporting foam layer adhered to the resilient foam layer. In both embodiments, the resilient layer absorbs the energy of deformation of the aluminum outer hull layer, restores the aluminum outer hull to its original shape when the deforming stresses are removed. An inner rigid sheet that is adhered to the innermost inward surface of a foam layer without direct mechanical attachment to the outer hull layer, and the laminate structure provides sufficient structural support to the hull to not require additional cross-supports. A rigid, self-supporting open-hulled aluminum boat can be contructed from either of these laminate structures. Transverse bulkheads are attached to the inner rigid sheet to support a deck.

This application is a continuation of U.S. Pat. application Ser. No.001,811 filed Jan. 8, 1987, now issued as U.S. Pat. No. 4,739,722 onApr. 26, 1988.

TECHNICAL FIELD

The present invention relates to boat hulls, and more particularly, toopen-hulled aluminum boats.

BACKGROUND OF THE INVENTION

It is known in the prior art to build aluminum-hulled boats made fromsheet aluminum. Since they are light, such boats have found greatpopularity for various aquatic activities, such as fishing andmotorboating. Because of their light construction, aluminum boatstypically need bulkheads and other cross-braces extending transverselybetween the opposing hull sides in order for the boats to besufficiently rigid. In many boats, the cross-braces also serve as benchseats. These cross-braces are typically held in place by rivetsprojecting through holes in the thin-skinned hull below or close to thewater line. Unfortunately, rivets are also potential leak sites. Becauseof the need to include the cross-braces and use many rivets,construction of such aluminum-hulled boats is labor intensive and theboats are consequently more expensive. The cross-braces also add weightto the boat. As such, it is not possible to make a light aluminum hullboat with an open hull design since cross-braces are required to achievesufficient strength. As noted above, these cross-braces frequently takethe form of bench seats, even in boat designs where several midships'bench seats are not desired and an open hull with a single swivel seatand console arrangement is preferred.

With conventional construction of aluminum boats, the requirement to addbench seats as cross-braces, and the mechanisms sometimes used todistribute the load placed on the seats to the hull bottom so as not tobe all supported by the rivet points to the hull sides, render itinfeasible to add an interior flat deck to the boat. The extra weightand the necessary riveting of floor supporting braces to the boat hullfurther deter the use of interior decking. As such, the user must walkon the curved interior side of the hull bottom, which is lesscomfortable and provides a less stable than desired platform on which tostand or place equipment.

While aluminum sheets used for boat hulls are relatively light, theyalso have a relatively high modulus of elasticity. Accordingly,trailerable aluminum-hulled boats frequently suffer permanentdeformations to their hulls at the trailer support points. This is dueto the stresses produced by the trailer supports applying largelocalized pressures against the hull. The problem is more severe thegreater the weight of the hull and the more articles which are in orattached to the hull while being trailered, such as an outboard motor.The problem is compounded when the boat, after loaded on the trailer, isused to carry extra weight, such as fishing, camping and other sportinggear. As a result of the susceptibility to permanent deformation,aluminum boat manufactures recommend users never load their boats ontrailers of the type where rollers support the boat hull. Although mostmodern trailers use rollers since they are more convenient and make boatloading easier and safer, the limited number of rollers used apply toogreat a concentration of force on the hull. Thus, aluminum boat ownersare relegated to using the old style bunk trailers which support theboat hull on long, flat planks usually covered with a soft material.

Not only are hull deformations unsightly, but they lead to a decrease inoperating efficiency due to the increased hull drag. In addition,flexing at these points of deformation can lead to hull failure andleakage through nearby rivet holes.

Another problem common to aluminum hull boats is the vibration, noiseand general pounding of the water on the hull which is transferred tothe boat occupants, thus making for a less enjoyable and more fatiguingboat ride.

While it is known in the prior art to use foams in certain boatconstructions to provide additional flotation and to deaden sound, thelow density foams used tend to deteriorate due to wave impact andvibration. As a result, these low density foams are not recommended foruse in hulls of planing boats.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a laminate boat hullstructure capable of returning to its unstrained shape after beingsubjected to concentrated stresses.

It is another object of the present invention to provide a laminate boathull structure with a rigid inner sheet that will support the fastenerswithout fastening through the outer layer.

It is a further object of the present invention to provide a rigidopen-hulled aluminum boat that does not need internal cross-braces.

It is still another object of the present invention to provide anopen-hulled aluminum boat that can have internal fixtures, such asdecks, without the need to apply fasteners through the outer hull.

In general, the laminate boat hull structure of the present inventioncomprises a deformable high modulus outer hull layer having apredetermined unstrained shape and a resilient foam layer adhered to aninward side of the outer layer. The resilient foam layer has asufficiently low compressive modulus to absorb energy through the outerlayer when the outer layer is deformed from its unstrained shape andreleases the energy to the outer layer when the stress is removed,thereby forcing the outer layer to return to its unstrained shape. Inone embodiment, the laminate structure can further comprise a supportingfoam layer adhered to the resilient foam layer, the supporting foamlayer being harder than the resilient foam layer. The laminate structurecan also comprise an inner rigid sheet adhered to an inward surface ofthe outermost foam layer, the structure being substantiallyvibrationally isolated from the outer hull layer and out of directmechanical engagement with the outer hull layer.

The invention also comprehends an open-hulled aluminum boat having apredetermined unstrained outer shape, the boat having a watertight,deformable aluminum outer hull layer. The boat further has a resilientfoam layer adhered to an inward side of the outer hull layer, theresilient foam layer damping boat vibrations and absorbing energythrough the outer hull layer when the outer hull layer is deformed fromits unstrained shape and releasing the energy to the outer hull layerwhen the stress is removed. The foam thereby forces the outer hull layerto return to its unstrained shape. The open-hulled aluminum boat alsoincludes an inner rigid sheet, adhered to an inward side of theresilient foam layer and vibrationally isolated from the outer hulllayer and out of direct mechanical engagement therewith. The combinedresilient foam layer and inner rigid sheet provide sufficient structuralstrength support to the outer hull layer to avoid the need forcross-bracing extending between the hull sides. The open-hulled aluminumboat can further comprise one or more transverse bulkheads, thebulkheads being fastened to the inner rigid sheet and supporting a deckabove the inner rigid sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an aluminum boat built with a firstembodiment of a laminate structure of the present invention;

FIG. 2 is an enlarged, cross-sectional view of the laminate structureshown in FIG. 1;

FIG. 3 is a cross-sectional view of an open-hulled aluminum boat builtwith a second embodiment of the laminate structure of the presentinvention; and

FIG. 4 is an enlarged, cross-sectional view of the laminate structureshown in FIG. 3.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to FIG. 1 of the drawings, an aluminum boat 10 is shownas comprising a watertight, deformable high modulus aluminum outer hulllayer 12. The outer hull layer 12 can typically be made from a singlesheet or joined panels of aluminum, approximately 0.063 inches thick,thereby providing a watertight layer. The upper edges of outer hulllayer 12 can be fitted with a gunwale 14 made from extruded aluminum andfastened by rivets to the outer hull layer 12.

As best shown in the enlarged, cross-sectional view of FIG. 2, the hull,according to the present invention, is formed of a laminate structureincluding the outer hull layer 12 and a resilient foam layer 16 adheredto an inward surface of outer hull layer 12. An adhesive layer 18 isprovided between layers 12 and 16. The resilient foam layer 16 can beconsiderably thicker than outer hull layer 12, for example, one inchthick. The foam layer 16 serves not only to dampen boat hull vibrationsand noise and to provide some flotation, but also serves to restore theouter hull layer 12 to its unstrained shape when subjected toconcentrated stresses such as when loaded on a roller trailer fortransit. This latter function is served by selecting a resilient foamlayer 16 having sufficient resiliency, low compressive modulus andthickness to absorb energy transmitted through the outer hull layer asthe outer hull layer is deformed from its unstrained shape under a forceotherwise sufficient to permanently deform the aluminum outer hulllayer, and then to release the energy to the outer hull layer when thedeforming stress is removed. By so distributing the loading, nopermanent deformation is realized. The resilient foam layer 16 can beselected with sufficient resiliency to handle the maximum anticipatedpoint loading on the outer hull layer, such as from a roller of a rollertrailer so as to allow the aluminum to deform, but not past its elasticlimit which would cause permanent deformation. The effective yieldstrength of the hull structure is thereby increased. The resilient foamlayer 16 can be manufactured of Voltek Minicell/Volare or DOW ethafoamor a cross-linked polyfoam.

The resilient foam layer 16 also serves as a shock absorber to reducethe effect of wave pounding on the boat occupants and to deaden noise,thus providing a more enjoyable ride. Since the foam used is arelatively soft foam, the degradation realized with rigid foams whenused in planing boats due to wave impact does not occur. Anotheradvantage of the soft foam is that it can be easily deformed to matchthe shape of the boat hull and to match irregularities in the surface towhich it is to be adhered. This promotes good contact for bonding to thehull layer 12.

The laminate structure in FIG. 2 further includes an inner rigid sheet20 that is adhered to an inward side of resilient foam layer 16 by anadhesive layer 22. The inner rigid sheet 20 can, for example, be analuminum sheet 0.050 inches thick, although other sheet materials, suchas rigid plastic, can be used as well. As will be described in moredetail below, with this laminate structure, a sufficient structuralsupport is provided to the outer hull layer 12 so that an open-hulledboat construction is possible without requiring cross-braces extendingbetween and fastened to the hull sides. The laminate structure serves asa structural beam, but yet allows the hull bottom to work as it engagesthe waves. Much as with the currently popular flexible, rubber boats,the aluminum boat 10 of the present invention achieves increasedstrength and wave handling capability through its increased flexibilityover conventional aluminum boats using rigid cross-bracing/framing. Theapproach is contrary to conventional teachings to make aluminum boatsstronger by making them more rigid through increasing the rigidity ofthe framing and the wall thickness of the aluminum hull used. By usingthe laminate structure, the foam layer 16 and the rigid but yet somewhatflexible cover sheet 20 give and allow movement of the hull in responseto wave impact. Since no rivets or rigid cross-braces are used, themovement does not affect the integrity of the hull. The energy of thewave impact and even point loading from trailer rollers is distributedto an enlarged area and absorbed by the foam and given back to the hullto restore it to the unstrained shape.

Returning to FIG. 1, it can be seen that aluminum boat 10 can beconstructed with the resilient foam layer 16 being formed by adheringseparate left and right side elongated resilient foam layers 24 and 26,respectively, to the left and right inward surfaces 27a and 27b of thebottom of the outer hull layer 12. Next, the inner rigid sheet 20 isformed by a pair of left and right side elongated inner rigid sheets 28and 30, respectively, which are adhered over the corresponding left andright side resilient foam layers 24 and 26. The inner rigid sheets 28and 30 are cut to size so that their adjacent edges are spaced apartfrom each other and their outer edges are spaced apart from the outerhull layer 12 forming the sides of aluminum boat 10. The resilient foamlayers 24 and 26 extend substantially the full length of the boat 10,and the inner rigid sheets 28 and 30 extend coextensive therewith.

Next in the construction of the aluminum boat shown in FIG. 1, a pair ofleft and right side elongated resilient foam layers 34 and 36,respectively, are adhesively attached to the left and right inwardsurfaces 37a and 37b of the side panels of the outer hull layer 12.Then, a pair of left and right elongated inner rigid sheets 38 and 40,respectively, are adhered over the corresponding left and right sideresilient foam layers 34 and 36. To maximize the degree of vibrationisolation of inner rigid sheets 38 and 40 from the outer hull layer 12,rigid sheets 38 and 40 should not contact the inner rigid sheets 28 and30 or the outer hull layer 12. If desired, the exposed upper edge of thelaminate structure adhered to the side panels of the aluminum boat canbe capped and thereby protected by Z-brackets 42 and 44, which are eachheld in place by being attached to the gunwale 14.

The aluminum boat 10 construction, as described above, exhibitssufficient rigidity to require little, if any, cross-bracing between thehull sides even when used in a high speed planing boat. As such, theusual cross-bracing can be eliminated and the weight and manufacturingcost associated therewith eliminated. No additional internal framing isrequired. Moreover, the need to rivet through the outer hull layer 12 ator below the water line no longer exists. This results in substantialmaterial and labor savings, and produces a more desirable and betterperforming boat.

If it is desirable to provide the boat 10 with interior decking, such asto build a boat using a freestanding steering console and a swivel chair(not shown), a deck supporting cross-member 32 can be attached to theinner rigid sheets 28 and 30 using fasteners, such as blind rivets 36. Arigid deck 48 may then be fastened to the cross-member 32 and fixturesmay be fastened to the deck. By using the hull laminate structure of thepresent invention, it is possible to provide a flat deck and attachfixtures to the interior of boat 10 without piercing the outer hulllayer 12. Since the basic hull construction is lighter sincecross-braces are not required, the additional weight of the decking isacceptable.

The cross-member 32 can be made from aluminum or any other suitablematerial, and the deck 48 can be made from plywood. The deck 48 can beattached to cross-member 32 by fasteners 50, for example, self-threadingscrews. While not necessary for the construction of most boats, thecross-supports 32 also serve to provide additional cross-bracing for theouter hull layer 12 without riveting through the outer hull layer andwhile totally inhibiting the beneficial flexibility that the laminatestructure of the present invention provides.

It has been found that forces that would otherwise deform the outer hulllayer 12 from its unstrained shape are distributed throughout theresilient foam layer 16. When the stresses to outer hull layer 12 areremoved, the forces distributed within resilient foam layer 16 thencounteract the deformation of outer hull layer 12 from the interior ofthe hull, restoring the layer 12 to its unstrained shape. In addition,resilient foam layer 16 serves to vibrationally isolate outer hull layer12 from the interior of the hull and to absorb the energy of waveimpact, thereby providing a substantially smoother, quieter, and softerride to the occupants of the boat. Similarly, the resilient foam layerabsorbs the energy imparted to the outer hull layer 12 by boat trailerrollers, even when travelling over bumpy roads with the boat loaded withequipment thus preventing damage to the hull. In both situations, theabsorbed energy is also prevented from causing stress and strain induceddeterioration on any aluminum seams making up the outer hull layer 12,whether they be welds, rivets or other means for mechanically joiningthe aluminum sheet panels comprising many hulls.

In FIG. 3, an alternative embodiment of the open-hulled aluminum boat isshown, and indicated by reference numeral 52. The boat 52 is constructedusing another embodiment of the laminate structure of the presentinvention. An enlarged, cross-sectional view of this embodiment is shownin FIG. 4, and includes a resilient foam layer 54 adhered to an inwardside of the outer hull layer 12 by an adhesive layer 56. In thepresently preferred embodiment, resilient foam layer 54 is 3/8 inchthick. A supporting foam layer 58 is adhered to an inward surface of theresilient foam layer 54 through an adhesive layer 60. The supportingfoam layer 58 is chosen to be harder and thicker than resilient foamlayer 54, and in this embodiment is one inch thick. An inner rigid sheet20 is adhered to an inward surface of supporting foam layer 58 by anadhesive layer 62. By using two foam layers with different stiffnessesand other properties, a laminate structure can be achieved withdifferent characteristics. For example, a harder, more brittle foam maybe used as the supporting foam layer 58 to realize its advantages, whilea softer foam is used as the resilient foam layer 54 to provide theadvantages described above and also to protect the harder foam fromdeterioration.

Referring again to FIG. 3, open-hulled aluminum boat 52 can beconstructed by separately adhering resilient foam layer 54, thensupporting foam layer 58, and finally inner rigid sheet 20, one to thenext, using left and right side sheets, in a manner similar to thatdescribed for the construction of boat 10 of FIG. 1. Alternatively, thelaminate of resilient foam layer 54, supporting foam layer 58, and innerrigid sheet 20 can be preassembled. The preassembled laminate can thenbe cut to proper shape and adhered to an inward surface of outer hulllayer 12 to form the desired laminate structure.

FIGS. 1 and 3 show the laminate structure of the present inventionapplied to the bottom and side inward surfaces of outer hull layer 12.It will, however, be apparent to those skilled in the art that thelaminate structure need only be applied to selected portions of theinward surface of outer hull layer 12, for example, the inward surfacesof the bottom of the outer hull layer 12. While it is desirable to use alaminate structure which extends the full length of the boat, shortersections may be used, and less than the entire hull length may beconstructed with the laminate structure.

It will be appreciated that, although specific embodiments of theinvention have been described herein for purposes of illustration,various modifications may be made without departing from the scope ofthe invention. Accordingly, the invention is not limited except by theappended claims.

I claim:
 1. A laminate boat hull structure capable of returning to itsunstrained shape after being subjected to concentrated stresses, thestructure comprising:a deformable, high modulus outer layer having apredetermined unstrained shape; a preformed resilient and flexible foamlayer adhered to the inward side of the outer layer, the resilient foamlayer having a sufficiently low compressive modulus to substantiallyabsorb energy through the outer layer when the outer layer is performedfrom its unstrained shape by a concentrated stress and release theenergy to the outer layer when the stress is removed, to force the outerlayer to return to its unstrained shape; and an inner rigid sheetadhered to the resilient foam layer.
 2. The laminate boat hull structureof claim 1, wherein the inner rigid sheet is made from aluminum.
 3. Thelaminate boat hull structure of claim 1, further comprising:a supportingfoam layer adhered to the resilient foam layer, the supporting foamlayer being harder than the resilient foam layer; and the inner rigidsheet being adhered to the supporting foam layer.
 4. The laminate boathull structure of claim 3, wherein the supporting foam layer is thickerthan the resilient foam layer.
 5. The laminate boat hull structure ofclaim 3, wherein the inner rigid sheet is made from aluminum.
 6. A boathaving a predetermined, unstrained outer shape, comprising:a watertight,deformable high modulus outer hull; a resilient and flexible foam layerpreformed prior to positioning within the outer hull and adhered to aninward side of the outer hull, the resilient foam layer having asufficiently low compressive modulus to substantially dampen boatvibrations and absorb energy through the outer hull when the outer hullis deformed from its unstrained shape and release the energy to theouter hull when the stress is removed, to force the outer hull to returnto its unstrained shape; and an inner rigid sheet, adhered to an inwardside of the resilient foam layer and substantially vibrationallyisolated from the outer hull, the combined resilient foam layer andinner rigid sheet providing structural support for the outer hull undernormal loading during use.
 7. The boat of claim 6, wherein the innerrigid sheet is made from aluminum.
 8. The boat of claim 6, furthercomprising one or more transverse bulkheads, each bulkhead beingfastened to the inner rigid sheet and free of fastening points to theouter hull.
 9. The boat of claim 8, further comprising a deck supportedaway from the inner rigid sheet by at least one of the one or moretransverse bulkheads.
 10. A boat having a predetermined, unstrainedouter shape, comprising:a watertight, deformable high modulus outer hulllayer; a resilient and flexible foam layer preformed exterior of andprior to positioning within the outer hull layer and adhered to aninward side of the outer hull layer, the resilient foam layer havingsufficiently low compressive modulus to substantially dampen boatvibrations and absorb energy through the outer hull layer when the outerhull layer is deformed from its unstrained shape and release the energyto the outer hull layer when the stress is removed, to force the outerhull layer to return to its unstrained shape; a supporting foam layeradhered to an inward surface of the resilient foam layer, the supportingfoam layer having a hardness and thickness selected to provide thedesired passenger comfort or hull rigidity; and an inner rigid sheet,adhered to an inward side of the supporting foam layer and substantiallyvibrationally isolated from the outer hull layer.
 11. The boat of claim10, wherein the rigid inner sheet if made from aluminum.
 12. The boat ofclaim 10, further comprising one or more transverse bulkheads, eachbulkhead being fastened to the inner rigid sheet and out of directcontact with the outer hull layer.
 13. The boat of claim 12, furthercomprising a deck supported away from the inner rigid sheet by at leastone of the one or more transverse bulkheads and out of direct contactwith the outer hull layer.
 14. A rigid, self-supporting open-hulledboat, comprising:a watertight, deformable high modulus hull havingbottom and side outer panels extending between a bow and a transom; aplurality of preformed resilient and flexible foam layers, each of theresilient foam layers being adhered to an inward surface portion of oneof the bottom or side outer panels; and a plurality of contiguous innerrigid sheets, each of the rigid sheets being adhered to an inwardsurface of one of the resilient foam layers and substantiallyvibrationally isolated from and out of direct mechanical engagement withthe outer panel to which the corresponding one resilient foam layer isadhered, each of the foam layers having a sufficiently low compressivemodulus to substantially isolate the inner rigid sheets fromconcentrated forces impinging on the outer panels during normal usage.15. The rigid, open-hulled boat of claim 14, wherein each of the innerrigid sheets is made from aluminum.
 16. The rigid, open-hulled boat ofclaim 14, further comprising one or more transverse bulkheads, eachbulkhead being fastened to the inner rigid sheet and out of directmechanical engagement with the outer panels.
 17. The rigid, open-hulledboat of claim 16, further comprising a deck supported away from theinner rigid sheet by at least one of the one or more transversebulkheads and out of direct mechanical engagement with the outer panels.18. A rigid, self-supporting open-hulled boat, comprising:a watertight,deformable high modulus hull having bottom and side outer panelsextending between a bow and a transom; a plurality of preformedresilient and flexible foam layers, each of the resilient foam layersbeing adhered to an inward surface portion of one of the bottom or sideouter panels; a plurality of preformed contiguous supporting foamlayers, each of the supporting foam layers being adhered to an inwardsurface of one of the resilient foam layers; and a plurality ofcontiguous inner rigid sheets, each of the rigid sheets being adhered toan inward surface of one of the supporting foam layers and substantiallyvibrationally isolated from and out of direct mechanical engagement withthe outer panel to which the corresponding one resilient foam layer isadhered, the resilient foam layer having a sufficiently low compressivemodulus to substantially isolate the inner rigid sheets formconcentrated forces impinging on the outer panels during normal usage.19. The rigid, open-hulled boat of claim 18, wherein each of the innerrigid sheets is made from aluminum.
 20. The rigid, open-hulled boat ofclaim 19, further comprising one or more transverse bulkheads, eachbulkhead being fastened to the inner rigid sheet and out of directmechanical engagement with the outer panels.
 21. The rigid, open-hulledboat of claim 20, further comprising a deck supported away from theinner rigid sheet by at least one of the one or more transversebulkheads and out of direct mechanical engagement with the outer panels.22. A method for constructing a boat having a predetermined, unstrainedouter shape, comprising:providing a watertight, deformable high modulusouter hull; providing a resilient and flexible foam layer preformedexterior of and prior to positioning within the outer hull, theresilient foam layer being selected with a sufficiently low compressivemodulus to substantially absorb the energy of concentrated forcesdeforming the outer hull from its unstrained shape during normal usage;adhering the resilient foam layer to an inward side of the outer hull,the resilient foam layer dampening boat vibrations and absorbing energythrough the outer hull when the outer hull is deformed from itsunstrained shape and releasing the energy to the outer hull when thestress is removed, thereby forcing the outer hull to return to itsunstrained shape; providing an inner rigid sheet; and adhering the innerrigid sheet to an inward side of the resilient foam layer insubstantially vibrational isolation from the outer hull, the combinedresilient foam layer and inner rigid sheet providing structural supportfor the outer hull under normal loading during use.
 23. The method ofclaim 22, further including:providing one or more transverse bulkheads;attaching each of the bulkheads to the inner rigid sheet and free offastening points to the outer hull; providing a substantially planardeck; and attaching the deck to one or more of the transverse bulkheadsfree of fastening points to the outer hull.